Development of T cell memory in human Trypanosoma cruzi infection Trypanosoma cruzi-infected subjects with long-term (>20 years) infections have relatively modest CD4+ and CD8+ T cell responses to T. cruzi proteins/peptides and the CD8+ T cell population in these subjects shows signs of exhaustion and senescence, consistent with the persistence of infection in these individuals. The frequencies of T. cruzi-specific T cells were also found to correlate with the severity of chronic Chagas disease. Based upon these results, it may be hypothesized that in the face of the persistence of stimulating antigen the T. cruzi-specific and the overall T cell compartment is eventually driven to exhaustion, exhibits a low frequency of competent parasite-specific T cells and predisposes the subjects for disease progression. One prediction of this hypothesis is that individuals with shorter-term infections would have more robust T cell responses and fewer senescent/exhausted T cells. To test this prediction, the present project proposes to measure the quality and magnitude of T. cruzi-specific T cell response responses and the degree of immune exhaustion of the overall CD4+ and CD8+ T cell compartments in children between the ages of 6 and 14 with evidence of T. cruzi infection. The effect of treatment with benznidazole on humoral and cellular T cell responses during the early chronic phase of T. cruzi infection will be also investigated. Sera and PBMC will be obtained prior and after different time points post treatment with benznidazole. IL-2/IFN- gamma/TNF-a/granzyme B-secreting CD4+ and CD8+ T cells specific for T. cruzi proteins/peptides will be measured by ELISPOT and intracellular staining assays. The expression of CD27, CD28, CD57 and the rate of apoptosis on the total CD4+ and CD8+ T cell compartments in these same subjects will be determined as parameters of immune exhaustion while the evaluation of central vs. effector memory profile of the overall T cell compartment will be examined by the expression of CD62L and CCR7. Antibody titers to recombinant parasite proteins will be quantified by Bioplex assays. Completion of these studies will provide valuable information on the immunological consequences of long-term T. cruzi infection. Importantly, it will also determine whether treatment with benznidazole might be more effective in shorter-term infections because of a less degree of immune exhaustion. The establishment of a relationship between T cell response and the effectiveness of BZ treatment, would be beneficial for developing and testing new therapeutic interventions and will strongly support arguments to treat T. cruzi-infected subjects as early as possible and not only in children under 14 years of age, as officially recommended at present.